1. Field of the Invention
The present invention relates to a Single Photon Emission CT (SPECT) apparatus.
2. Description of the Related Art
Nuclear medicine is medicine for dosing a drug marked by radioactive isotopes (hereinafter, “RIs”) in a patient and imaging an internal RI distribution of the RIs to perform diagnosis. In a nuclear medicine diagnostic apparatus, an apparatus for imaging a three-dimensional distribution of the internal RIs is a Single Photon Emission CT (hereinafter, SPECT) apparatus.
In the SPECT apparatus, filter processing is often applied to collected data of two-dimensional projection distribution to reduce a noise component and correct spatial resolution. It is effective to carry out the filter processing to projection data before reconfiguration.
The filter processing is described in the following document: Edholm P E, Lewitt R M and Lindholm B: Novel properties of the Fourier decomposition of the sinogram. International Workshop on Physics and Engineering of Computerized Multidimensional Imaging and Processing. Proc of SPIE, 671, 8-18, 1986.
One of causes of a fall in spatial resolution is an incidence width of a gamma ray (see FIG. 4). Incidence widths w1 and w2 change according to distances d1 and d2 between a radiation source and a detector. Spatial resolution of a radiation source S2 farther from a detector 3 than a radiation source S1 is lower than that of a radiation source S1.
However, at a stage of the two-dimensional projection distribution data before reconfiguration, since the distances d1 and d2 cannot be separated, it is impossible to effectively correct the spatial resolution.